The invention relates to a method for manufacturing constant velocity joints, and more particularly to the manufacture of an outer race for a constant velocity joint.
German Offenlegungsschrift 37 12 301 (German ""301) discloses a press tool for plastic deformation of a preform having a cavity open on one side to produce non-undercut axial ball tracks and cage guide surfaces. The preform is received in a female tool and the shaping of the wall regions is then performed by a male, or inner, tool with the application of pressure.
In German ""301, the male tool consists of an inner die having individual radial ribs which reach through segments of a sleeve die to provide a forming surface which is closed in the circumferential direction. The joint between the two arts of the male tool is always in the transition between the all track forming region and the cage guide surface forming region.
The part of the male tool for making the ball tracks is formed by a one-piece solid tool part which can accept large forces without distortion or change in shape. This makes it possible to shape the ball track portions so precisely that no finishing operation is needed in these regions.
The intervening undercut cage guide surface regions are formed by the outwardly crowned segments of the sleeve die of the male tool, the segments of which, after removal of the inner die, can be removed from the finished workpiece by springing them radially inwardly.
The known press tool has the disadvantage that the two-piece inner tool is extremely complex and costly to manufacture and, owing to the parting surfaces formed between the two parts of the tool, namely, the inner die and the sleeve die, has increased susceptibility to wear.
A further disadvantage is that the tolerances required for making the forming tool in two parts necessarily lead to an increase in the workpiece tolerances, that is to say, the current tool tolerances must be added to the specified workpiece tolerances.
German Offenlegungsschrift 42 14 444 (German ""444) discloses a method for the manufacture of ball sockets for constant velocity joints wherein a cup-shaped blank is progressively locally plastically deformed radially as a function of time, with plastic reduction in section, to shape its inner form against a profiled mandrel which in the circumferential direction is corrugated and which in the axial direction has different convex curvatures which vary, preferably segmentally, around the circumference. The profiled mandrel used here is multipart and consists of radially separable profiled mandrel segments.
The German ""444 method also has the disadvantage that the profiled mandrel used, because of its multipart design, is complex and expensive to manufacture and is susceptible to wear. A further disadvantage is that the tolerances required for the division of the forming tool in two necessarily lead to increase in the workpiece tolerances, i.e., the current tool tolerances must be added to the specified workpiece tolerances.
The object of the invention is to provide a method for the manufacture of outer parts of constant velocity joints of the kind referred to in which the disadvantages of the known manufacturing process which have been pointed out are avoided and in which ball tracks can be made either without or with undercuts.
To this end, in accordance with the invention, a method and tool are provided for manufacturing an outer race for a constant velocity joint by plastic deformation of a preform having a cavity open on one side to produce axial ball tracks and cage guide surfaces. The preform is inserted within an outer tool. An inner tool is inserted within the preform. The insert is wobble pressed with the inner tool.
As a result of using as the inner tool a one-piece pressing die having segments with different convex curvatures and having a particular external contour, which is introduced into the cavity and which, by wobble pressing, produces the desired final form of the inner wall regions for the ball track and the cage guide surfaces in a plurality of locally progressive revolution, a very robust forming tool is provided which leads to improved workpiece tolerances.